A tire withstands the weight of an automobile, reduces impact from the road, and transfers driving force or braking force of an automobile to the ground.
In general, a tire is a complex of fiber/steel/rubber, and has a structure as shown in FIG. 1.
Tread (1): a part contacting the road. It should afford frictional force required for driving, have good wear resistance, withstand external impact, and have low heat production.
Body ply, or carcass (6): a cord layer in the tire. It should support the vehicle weight, withstand impact, and have high fatigue resistance to bending and stretching exercises while running.
Belt (5): located between the body plies, consists of steel wire in most cases, reduces external impact, and maintains a wide tread to afford excellent vehicle running stability.
Side wall (3): a rubber layer between a part below a shoulder (2) and bead (9). It protects the inner body ply (6).
Inner liner (7): located inside the tire instead of a tube, and prevents air leakage to enable a pneumatic tire.
Bead (9): square or hexagonal wire bundle formed of rubber-coated steel wire. It positions and fixes the tire to a rim.
Cap ply (4): a special cord located on a belt of a radial tire for some cars. It minimizes movement of the belt during running.
Apex (8): triangular rubber filler used to minimize dispersion of the bead, reduce external impact to protect the bead, and prevent air inflow during forming.
A tubeless tire where high pressure air of 30 to 40 psi is injected is commonly used without using a tube, and to prevent air leakage during automobile running, an inner liner having a high gas barrier property is positioned as the inner layer of the carcass.
Previously, a tire inner liner including rubber such as butyl rubber, halobutyl rubber, and the like having relatively low air permeability as a main ingredient was used, but to achieve a sufficient gas barrier property of the inner liner, the rubber content or inner liner thickness should be increased.
However, if rubber content and tire thickness are increased, total weight of the tire may be increased and automobile mileage may be degraded.
Further, since the rubber ingredients have relatively low heat resistance, air pockets may be generated between rubber in the inner surface of a carcass layer and the inner liner, or the shape or properties of the inner liner may be changed in a vulcanization process of a tire or in an automobile running process during which repeated deformations occur at a high temperature.
To bond the rubber ingredients to a carcass layer of a tire, a vulcanizer should be used or a vulcanization process should be applied, but sufficient adhesion may not be secured therewith.
Therefore, various methods have been suggested to decrease the thickness and weight of the inner liner to increase mileage and reduce changes in the shape or properties of the inner liner during vulcanization of a tire or running, and the like.
However, previously known methods have limitations in maintaining excellent air permeability and formability of a tire while sufficiently decreasing the thickness and weight of the inner liner.
In addition, the inner liner manufactured by the previously known method exhibited property degradation or generated cracks and the like in a tire manufacturing process during which repeated deformations occur at a high temperature, or in an automobile running process during which repeated deformations occur and high heat is generated.